Atom: https://atom.io/
XtraFinder: http://www.trankynam.com/xtrafinder/
iTerm2: https://www.iterm2.com/
SourceTree: https://www.sourcetreeapp.com/
Asepsis: http://asepsis.binaryage.com/ (This prevents creation of new .DS_Store files - nice but doesn't work anymore with OS X 10.11)
homebrew, npm, git, bash aliases..
Above all I think the most essential tool for me is Spectacle https://www.spectacleapp.com/
Homebrew is also a requirement.
Iterm2 to replace the default terminal. I also added this https://github.com/SebastienElet/iterm2-borderless.
Everything else is pretty developer specific in my opinion. I'd recommend Visual Studio Code for a text editor (if you don't already have a preference). It has built-in git integration and installing new plugins is trivial.
Install Xcode command line tools
xcode-select --install
verbose boot messages nvram boot-args="-v"
make Library visible chflags nohidden ~/Library
verify Time Machine backups tmutil comparehttps://duckduckgo.com/?q=setup%20mac%20for%20development
In the future if you want better help for a question like this, you should state whether you're familiar with UNIX or not, what type of development you do, what stack you develop for, what languages, what you have already done. etc.
alfred
Spectacle
Bartender
Textbar
Geektool
Xtools
Pushbullet
Mixmax menubar extension